Physical Science Chapter 3

Which of the following is not a unit of work?

Kilogram-meter

Units of Work

Newton-meter
Joule
Watt-hour

An object at rest may have

potential energy

A moving object must have which one or more of the following?

Kinetic Energy
Rest Energy
Momentum

When the momentum of a moving object is increased, there must also be an increase in which one ore more of the folllowing of the objects' properties?

Speed and Kinetic Enegry

The total amount of energy in the universe

cannot change

When the speed of a moving object is halved,

its momentum is halved

Two balls, one of mass 5kg and the other of mass 10kg, are dropped simultaneously from a window. When they are 1 m above the ground, the balls have the same

acceleration

A bomb droped from an airplane explodes in midair.

Its total kinetic energy increases

The operation of a rocket is based upon

conservation of linear momentum

A spinning skater whose ares are at her sides then stretches out her arms horizontally.

SHe spins more slowly

According to the principle of relativity, the laws of physics are the same in all frames of reference

At rest with respect to one another, moving toward or away from one another at constant velocity, and moving parallel to one another at constant velocity

The formula 1/2mv2 for kinetic energy

is the low-speed approximation to the correct formula

A spacecraft has left the earth and is moving toward Mars. An observer on the earth finds that, relative to measurements made when the spacecraft was at rest, its

length is shorter

The upper limit to the speed of an object with mass

is the speed of light

It is not true that

momentum is a form of energy

It is true that

light is affected by gravity
the mass of a moving object depends upon its speed
the maximum speed anything can have is the speed of light

Albert Einstein did not discover that

the acceleration of gravity g is a universal cosntant

Albert Einstein discovered that

the length of a moving object is less than its length at rest
light is affected by gravity
gravity is a warping of spacetime

The work done in hoding a 50-kg object at a height of 2 m above the floor for 10s is

0

THe work done in lifitng 30 kg of bricks to a height of 20 m is

5880J

A total of 4900J is used to lift a 50-kg mass. The mass is raised to a height of

10m

The work a 300-W electric grinder can do in 5.0min is

90kJ

A 150-kg yak has an average power output of 120W. The yak can climb a mountain 1.2 km high in

4.1h

A 40-kg boy runs up a flight of staris 4m high in 4s. His power output is

392 W

Car A has a mass of 1000kg and is moving at 60 km/h. Car B has a mass of 2000 kg and is moving at 30 km/h. The kinetic energy of car A is

twice that of Car B

A 1-kg object has kinetic energy of 1J relative to the ground when it is at a height of

0.102m

A 1-kg object has kinetic energy of 1 J when its speed is

1.4 m/s

The 2-kg blade of an ax is moving at 60 m/s when it strikes a log. If the blade penetrates 2 cm into the log as its KE is turned into work, the average force it exerts is

180 kN

A 1-kg ball is thrown in the air. WHen it is 10 m above the ground, its speed is 3m/s. At this time most of the ball's total energy is in the form of

rest energy

A 10,00-kg freight car moving at 2m/s collides with a stationary 15,00-kg freight car. the two cars couple together and move off at

0.8 m/s

A 30-kg girl and a 25-kg boy are standing on frictionless roller skates. The girl pushes the boy, who moves off at 1.0 m/s. The girl's speed is

0.83 m/s

An object has a rest energy of 1J when its mass is

1.1 times 10 -17 kg

The lighest particle in an atom is an atom is an electron, whose rest mass is 9.1 times 10 -31 kg. THe energy equivalent of this mass is appriximately

10 -13 J

SI unit of work

Joule